Liquid surface sensing devices that sense the liquid surface of a liquid have hitherto been known. In a device described in Patent Literature 1, an opening is formed in the ceiling of a fuel tank, with a lid closing the opening. A lead wire connects a liquid surface sensor having a sensing unit such as a hole IC or the like with an external device.
To improve the sealing properties between the fuel tank and the lid, it has been common in recent years to provide a rubber gasket between the fuel tank and the lid. However, such a gasket may suffer bleeding which is an exuding phenomenon of a liquid composition contained in the gasket, and such liquid composition may travel down the lead wire and adhere or bond to metals used in the sensing unit of the liquid surface sensing device, which may deteriorate the sensing unit or adversely affect the sensing results.